Over the past couple decade’s marijuana abuse has flourished in the United States. Some 50 million people in the United States have used for recreation purposes and 30% are chronic users. This has caused a need for testing individuals for drug use in the workplace as well as for legal purposes.

Many governments are coming to the understanding that driving or operating equipment under the influence of marijuana can be dangerous. (1, 2)

Marijuana use is the second highest reason for motor vehicle accidents in the United States. For this reason, many states have established limits for blood THC concentration when driving. (5) The issue here is that up till recently there hadn’t been many studies done on the accuracy of testing.

Most urine tests were not all that accurate before and there were no other options. In this article, I will discuss what we know and what is currently being used as well as results of the new studies being done. (1,2)

Are there any regulations or assistance in drug testing?

They are on the verge of creating specific regulations regarding testing for marijuana use.

They have various guidelines that can be useful as of now. These are shown below but are not limited to this list:

Technical Assistance publication Series (TAP series)

Drug testing in Child Welfare Practice and Policy Considerations.

Federal Guidelines for Opioid Treatment Programs.

A Guide to Substance Abuse for Primary Care Clinicians: Concise Desk Reference Guide. This also has a separate Quick Guide.

Alcohol and Drug Use Screening, Intervention, and Referral: Changing the Nation’s Approach to Comprehensive Healthcare.

How long does Marijuana (THC) stay in your blood (bloodstream)

Tests for Delta-9-tetrahydrocannanbiol (THC) metabolite.(1,2,5,7)

This metabolite is quickly broken down and transferred into fatty tissue.

Can be noted in the blood up to 4 days max.

Has been detected in brain and fatty tissue much longer than in blood serum.

Due to this fatty tissue storage, the amount of drug in the blood serum can waiver from day to day without further use. (See graph below)

Illegal levels of THC in the blood can be noted for up to 9 days after abstinence.

THC metabolites can show up in the blood serum of chronic users for up to 1 month. (5,7)

This test can tell the amount of drug used and if the person is currently intoxicated.

Due to the previous statement, this is currently the test of choice when performance is the reason for testing the client.

This test also will be positive if the client has been exposed to second-hand smoke. (1,2,7)

This test must be done in a laboratory setting with trained personnel.

These results can vary widely depending on the amount used and for how long.

All these facts show that having levels of THC metabolites in the blood does not always suggest recent use. (9)

Positive results could be due to fasting or exercise in a patient who at one time were chronic users. Caution should be taken when taking actions according to blood serum results.

As a matter of fact, studies have shown a significant increase in THC metabolites after 35 min of exercise. (11)

In this image, you can see the relation of the different THC metabolites and how long they were detected in the blood.

Graph source : http://www.ncbi.nlm.nih.gov

How long does Marijuana (THC) stay in your Saliva

Detects Δ9-tetrahydrocannabinol (THC) in the saliva

Exposure to second-hand smoke can give a false positive.

11-nor-9-carboxy-Δ9-tetrahydrocannabinol (THCCOOH) can also be tested and is not a component of cannabis smoke. Therefore the chance of false positive with second-hand smoke is decreased.

This type of testing can be used for:

Driving under the influence

Workplace performance

Counseling for drug treatment

Pain management situations

A major benefit to this type of testing is that it can be collected without the need of privacy from the client.

This form of collection is harder to tamper with.

There is a much lower risk for the transition to infectious disease when collecting saliva from the client.

A kit may include a device for collection as well as for storage to protect the specimen until time for testing.

A study showed that positive THCCOOH tests were evident up to 29 days in chronic use. (3,6,11)

How long does Marijuana stay in your Hair follicles

Detects various metabolites including

THC

THC-COOH

THC-OH

Cannabinol

Cannabidiol

Uses chromatography as well as mass spectrometry assays.

The process of THC metabolites entering the hair is through small capillaries and sweating.

Can be noted up to 3 months after exposure.

Does not only show use but also exposure to second-hand smoke.

The amount found in the hair can help to show the amount used. (1)

How long does Marijuana (THC) stay in your urine

Detects both Delta-9-tetrahydrocannanbiol (THC) metabolite and 11-nor-delta-9-THC carboxylic acid in the urine.

7 days with single use

10 days with chronic use

2 weeks for a casual user

Studies have suggested that all THC is excreted within five days of the last dose.

This includes those who may have only been exposed and don’t use the drug.

A benefit of this type of testing is that it can be done by lay persons and does not require laboratory equipment.

This cannot tell the amount of the drug used; it only shows positive or negative.

False-positive due to second-hand smoke would only occur if it was in a closed in space.

If all recommendations are followed correctly most studies show a 95% accuracy with urine testing for 9-carboxy-THC, and yet lab specialist requests that all positive tests be backed up by a different form of testing.

Many studies state that if the purpose of screening is work performance using a urine test will not be effective. (1,2)

On the contrary, if the history of marijuana use is the goal then the urine test is a good choice.

Caution should be taken with positive results for a client who is abstaining from use. These positives could be due to continued breakdown of metabolites from fat cells. (10)